Hilflos translates to "helpless". It's an interesting word because it conveys a strong emotional state, often used in situations where one feels overwhelmed or powerless.
In this song, Hansi Hinterseer sings, "Wie sie spricht, wie sie lacht, hat mich hilflos gemacht" (How she speaks, how she laughs, has made me helpless). He uses it to express how completely captivated and overwhelmed he is by his beloved, to the point of feeling utterly helpless in her presence. This dramatic use makes it a memorable and engaging word.
Hansi Hinterseer built a career on songs this uncomplicated, and "Du Bist Ein Engel Für Mich" doesn't try to be anything else. The whole song sits on one idea: "Wie sie spricht, wie sie lacht" [the way she speaks, the way she laughs] "Hat mich hilflos gemacht" [left me helpless]. That's the plot. There's no twist, no second verse where the mood turns dark, just a man listing what he likes about her, "Ich mag alles an ihr, so wie sie sich bewegt" [I like everything about her, the way she moves], circling back each time to "Du bist mein Engel für mich" [you are my angel for me].
It ends the way most Schlager singalongs do, with the words giving way to a long "la la la" refrain built for a room that already knows the tune. This one belongs on the dance floor at an Austrian Volksfest more than on headphones.